Thomas Balstrøm

Arsenic in Drinking-Water and Risk for Cancer in Denmark

Background Arsenic is a well-known carcinogen, which is often found in drinking-water. Epidemiologic studies have shown increased cancer risks among individuals exposed to high concentrations of arsenic in drinking-water, whereas studies of the carcinogenic effect of low doses have had inconsistent results. Objective Our aim was to determine if exposure to low levels of arsenic in drinking-water in Denmark is associated with an increased risk for cancer. Methods The study was based on a prospective Danish cohort of 57,053 persons in the Copenhagen and Aarhus areas. Cancer cases were identified in the Danish Cancer Registry, and the Danish civil registration system was used to trace and geocode residential addresses of the cohort members. We used a geographic information system to link addresses with water supply areas, then estimated individual exposure to arsenic using residential addresses back to 1970. Average exposure for the cohort ranged between 0.05 and 25.3 μg/L (mean = 1.2 μg/L). Cox’s regression models were used to analyze possible relationships between arsenic and cancer. Results We found no significant association between exposure to arsenic and risk for cancers of the lung, bladder, liver, kidney, prostate, or colorectum, or melanoma skin cancer; however, the risk for non-melanoma skin cancer decreased with increasing exposure (incidence rate ratio = 0.88/μg/L average exposure; 95% confidence interval, 0.84–0.94). Results adjusted for enrollment area showed no association with non-melanoma skin cancer. Conclusions The results indicate that exposure to low doses of arsenic might be associated with a reduced risk for skin cancer.

Generating a Danish raster-based topsoil property map combining choropleth maps and point information.

Abstract Geografisk Tidsskrift, Danish Journal of Geography 107(2):1–12, 2007 The Danish environmental authorities have posed a soil type dependent restriction on the application of nitrogen. The official Danish soil map is a choropleth topsoil map classifying the agricultural land into eight classes. The use of the soil map has shown that the maps have serious classification flaws. The objective of this work is to compile a continuous national topsoil texture map to replace the old topsoil map. Approximately 45,000 point samples were interpolated using ordinary kriging in 250 m x 250 m cells. To reduce variability and to obtain more homogeneous strata, the samples were stratified according to landscape types. Five new soil texture maps were compiled; one for each of the five textural classes, and a new categorical soil type map was compiled using the old classification system. Both the old choropleth map and the new continuous soil maps were compared to 354 independent soil samples. 48% of the 354 independent samples fell into the correct class in the old map; in the new map 60% fell into the correct class, which is a significant improvement. The verification also showed that 62% of the samples in the forest areas were correctly classified, although these areas were not classified in the old map. Furthermore, when both the old and the new map were compared cell-by-cell, 74% of the cells were classified as belonging to the same class. The new textural maps were tested against the textural properties of 631 independent samples, and the root mean squared error (RMSE) of this comparison was calculated and found to be in the range of 2.8 to 5.2.

On identifying the most time saving walking route in a trackless mountainous terrain

Abstract A procedure is presented to find the most efficient walking route to inspect 16 rain gauges within a mountainous location on the Faeroe Islands. Measured walking times on varying slopes and crossing shallow rivers were used as inputs to establish a friction-based cost surface. Subsequently, a cost path analysis led to identification of a web of least-cost paths between the locations. Finally, the most time-saving route to visit all rain gauges in one round trip from the base camp was found using network optimizing software.

Application of a new methodology for coastal multi-hazard-assessment & management on the state of Karnataka, India

This paper presents the application of a new methodology for coastal multi-hazard assessment & management under a changing global climate on the state of Karnataka, India. The recently published methodology termed the Coastal Hazard Wheel (CHW) is designed for local, regional and national hazard screening in areas with limited data availability, and covers the hazards of ecosystem disruption, gradual inundation, salt water intrusion, erosion and flooding. The application makes use of published geophysical data and remote sensing information and is showcasing how the CHW framework can be applied at a scale relevant for regional planning purposes. It uses a GIS approach to develop regional and sub-regional hazard maps as well as to produce relevant hazard risk data, and includes a discussion of uncertainties, limitations and management perspectives. The hazard assessment shows that 61 percent of Karnatakas coastline has a high or very high inherent hazard of erosion, making erosion the most prevalent coastal hazard. The hazards of flooding and salt water intrusion are also relatively widespread as 39 percent of Karnatakas coastline has a high or very high inherent hazard for both of these hazard types.

A method to identify potential cold-climate vine growing sites: a case study from Røsnæs in Denmark

Abstract Geografisk Tidsskrift Danish Journal of Geography 111(1):73–84, 2011 A method for surveying the suitability of cold climate vine growing sites in Denmark is presented with focus on limiting growth parameters. The four most important parameters are identified on the basis of literary studies and discussions with approximately 150 vine growers in Denmark. These are: i) Sum of growing degree days (SDD), ii) Risk of frost damage, Hi) Number of sunshine hours during growth season, and iv) Soil drainage. A two-step method based on GIS and already existing climate, soil, and topographic data was implemented. First the most suitable areas in Denmark for vine growing were located on the basis of nation-wide climatic data on the sum of degree days and risk of frost. Within the most suitable areas a detailed survey of the amount of sunshine, topography, drainage and soil was carried out on the Røsnœs peninsula in north western Zealand, and eight well-suited vine growing terroirs were identified of which three were highly recommended.

Role of landscape parameters in riverine run-off, and sediment and organic matter yield on Disko Island, West Greenland

Abstract Measurements of discharge and suspended sediment and organic matter yield from nine different drainage basins on the island Disko in central West Greenland were carried out in the period 19–30 July 1997. A series of landscape properties (glacier cover, altitude, slope, aspect and vegetation cover) were measured for each drainage basin from a digital elevation model and a satellite image. Principal Component Analysis and regression statistics have been used to examine which landscape parameters dominate the measured discharges and yields. It is concluded that differences in suspended sediment and organic matter yield between the drainage basins can be explained by the measured morphometric properties while differences in water run-off can not. Glacier cover percentage and percent area above 800 m a.s.l. were the most important parameters influencing suspended sediment and organic matter yield in the drainage basins on Disko during the study period.

Generation of a digital elevation model of Mols Bjerge, Denmark, and georeferencing of airborne scanner data

Abstract Geografisk Tidsskrift, Danish Journal of Geography 99: 35–45, 1999 The study compares various digital elevation models (DEM) and georeferencing methods for the purpose of orthorectifying airborne scanner data. The study was performed using topographical maps on the scale of 1:25,000 produced by the Danish National Survey and Cadastre and a Compact Airborne Spectrographic Imager (casi) image. The study area, was a topographically complex area in Denmark, Mols Bjerge. The generation of the digital elevation model was performed using a discretised thin plate spline technique modified to allow the fitted DEM to follow abrupt changes in the terrain. The accuracy of the DEM was primarily evaluated by comparing the original and the modelled contour lines. The georeferencing was performed using regional modified versions of polynomial distortion modelling and triangle warping, applying both ground control points and DEM features for panoramic and topographical correction in the process. It was concluded ...

Towards a second generation digital elevation model for Denmark

Abstract Geografisk Tidsskrift, Danish Journal of Geography 99: 27–34, 1999 In 1985 the first national digital elevation model (DEM) of Denmark was produced, based on 5 m contours from topographical maps with a scale of 1:50,000. Though improved during the last decade, it is obvious that the quality of this model is not sufficient for environmental assessments related to e.g. studies of overland flows. The Danish National Survey and Cadastre, which is responsible for the mapping of the Danish topographical surface is, therefore, presently working on a new DEM derived from a product, named TOP 10DK planned for release in the year 2001. This product will feature a second generation elevation model based upon 2.5 m contours and a significant number of measured topographic elements such as streams, lakes, roads and ditches. This paper will describe the current stage of constructing digital elevation models for Denmark. DEMs will then be considered as input to environmental modelling assessments and specificat...

The use of geographical information systems in the planning phase of a fieldwork project

Bai Strom, Thomas: The Use of Geographical Information Systems in the Planning Phase of a Fieldwork Project. Geografisk Tidsskrift 92:75–79. Copenhagen 1992. This article will demonstrate how a digital elevation model for a catchment area on the Faeroe Islands has been used in a geographical information system to select suitable sites for rain gauge mounting in order to reflect the orographic conditions. Furthermore, it will demonstrate how to identify one or more locations in the terrain, from where all the rain gauges are visible. The localization of such viewpoints may be of great value when selecting optimal positions for setting up a levelling instrument to determine the exact coordinates of the rain gauges.